Meniscal tears

Anatomy

There are two meniscii in the knee, the medial and lateral meniscus.The meniscii consist of cartilage and provide shock absorption and stability to the joint.The meniscii are attached to the capsule on the periphery and are vascularized in their outer 1/3. The inner 2/3's has no blood supply and no healing potential.

Injuries

The meniscii can be injured in many ways including activities as simple as arising from a seated position to more spectacular athletic injuries. If the tear is simple (not shredded) and in the vascular zone, meniscal repair is preferable to partial meniscectomy. Most injuries seem to occur in the avascular zones and are therefore irreparable. Loss of as little as 10% of the meniscus can lead to increased contact forces on the joint leading to changes in the articular cartilage that ultimately lead to degenerative arthritis.

Meniscal tear

Diagnosis

Meniscal tears can usually be diagnosed by means of history and physical exam. There will often be joint line tenderness, loss of motion and occasionally there may even be some swelling. All of these findings are not always present. X-rays do not show meniscii, but are useful for evaluating the bone and joint space. MRI is occasionally helpful but because of its limitations evaluating articular cartilage it is not often helpful in distinguishing articular cartilage from meniscal cartilage injuries which have similar histories and physical findings.

Treatment

Meniscal tears can lead to pain, locking, swelling and wear on the articular cartilage surfaces. Most tears will not respond to non-operative treatment. Arthroscopy is the treatment of choice for meniscal tears. The meniscus should be repaired whenever possible or minimal meniscectomy performed.To date there is no reliable meniscal replacement, allograft meniscal replacement may offer a promising alternative in the future. Most meniscal symptoms are reliably resolved with meniscectomy but continued high impact activity is not advisable due to the increased joint load leading to degenerativearthritis.